High geometric surface area catalysts for vinyl acetate monomer production

ABSTRACT

A catalyst includes a support, where the support includes an external surface, about 60 wt % to about 99 wt % silica, and about 1.0 wt % to about 5.0 wt % alumina. A catalytic layer is disposed within the support adjacent to the external surface, where the catalytic layer further includes Pd, Au, and potassium acetate (KOAc). In the catalyst, (a) the KOAc is from about 60 kg/m3 to about 150 kg/m3 of the catalyst; or (b) the catalytic layer has an average thickness from about 50 μm to about 150 μm; or (c) both (a) and (b). The catalyst also possesses a Brunauer-Emmett-Teller surface area of about 130 m2/g to about 300 m2/g and a geometric surface area per packed bed volume from about 550 m2/m3 to about 1500 m2/m3. The catalyst is highly active for the synthesis of vinyl acetate monomer and exhibits a high selectivity for vinyl acetate monomer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C. §371 of International Application No. PCT/US2016/043387, filed on Jul.21, 2016, which claims the benefit of U.S. Provisional PatentApplication No. 62/195,499, filed on Jul. 22, 2015, the entiredisclosures of which are incorporated herein by reference for any andall purposes.

FIELD

The present technology relates generally to the field of vinyl acetatemonomer production. More specifically, the catalysts are highly activefor the synthesis of vinyl acetate monomer and exhibit a highselectivity. The present technology also provides methods of making thecatalysts and processes involving the catalysts.

BACKGROUND

The vinyl acetate monomer (VAM) is a compound represented by thefollowing formula:

VAM is an important component in a wide variety of products, includingpolymers. VAM is also an important intermediate in coatings, textiles,paints, and other applications. For example, the polymer of VAM,polyvinyl acetate, is used in myriad applications including glues andadhesives.

SUMMARY

In an aspect, a catalyst is provided including a support that includesan external surface, about 60 wt % to about 99 wt % silica, about 1.0 wt% to about 5.0 wt % alumina, and a catalytic layer disposed within thesupport adjacent to the external surface, where the catalytic layerfurther includes Pd, Au, and potassium acetate (KOAc); aBrunauer-Emmett-Teller surface area of about 130 m²/g to about 300 m²/g;and a geometric surface area per packed bed volume (GSA/PBV) from about550 m²/m³ to about 1500 m²/m³, where (a) the KOAc is from about 60 kg/m³to about 150 kg/m³ of the catalyst; or (b) the catalytic layer has anaverage thickness from about 50 μm to about 150 μm, or (c) the KOAc isfrom about 60 kg/m³ to about 150 kg/m³ of the catalyst and the catalyticlayer has an average thickness from about 50 μm to about 150 μm. In someembodiments, the KOAc may be from about 65 kg/m³ to about 100 kg/m³ ofthe catalyst. In any of the above embodiments, the catalytic layer maybe from about 50 μm to about 550 μm thick.

In any of the above embodiments, the alumina may be from about 1.0 wt %to about 3.0 wt %. In any of the above embodiments, the Pd in thecatalyst may be from about 3 g/L to about 15 g/L. In any of the aboveembodiments, the Au in the catalyst may be from about 0.9 g/L to about 7g/L. In any of the above embodiments, the mass ratio of Pd to Au may befrom about 3.5:1 to about 2.0:1. In any of the above embodiments, thevoid fraction of the catalyst may be from about 35% to about 55%. In anyof the above embodiments, the catalyst may be in a shape including atleast one of cylindrical, spherical, tubular, polylobular, ring, star,saddle, fluted, or ridged. In any of the above embodiments, it may bethat with the exception of the catalytic layer, the support issubstantially free of Pd, Au, and KOAc.

In an aspect, method of making any one of the previously describedcatalysts is provided. The method includes permeating a support material(which includes an external surface with Pd and Au) to provide ametal-containing layer disposed within the support material adjacent tothe external surface. The support material includes about 60 wt % toabout 99 wt % silica, and about 1.0 wt % to about 5.0 wt % alumina, andthe metal-containing layer further includes Pd and Au.

In some embodiments, permeating the support material includes contactingthe support material with a salt solution that includes a salt of Pd, asalt of Au, or a mixture thereof. In any of the above embodiments, itmay be that subsequent to contacting with the salt solution, permeatingthe support material includes contacting the support material with abasic solution. In any of the above embodiments, it may be that themethod further includes a washing step subsequent to the permeatingstep. In any of the above embodiments, it may be that the method furtherincludes drying the support material subsequent to the permeating step.In any of the above embodiments, the drying subsequent to the permeatingstep may be conducted at a temperature from about 40° C. to about 250°C. In any of the above embodiments, the method may also include dryingthe support material subsequent to the washing step. In any of the aboveembodiments, the drying subsequent to the washing step may be conductedat a temperature from about 40° C. to about 250° C.

In any of the above embodiments, the method may further include exposingthe metal-containing layer to a reducing agent. The exposing step may beconducted at a temperature from about 15° C. to about 500° C.

In any of the above embodiments, the method may further includeimpregnating the metal-containing layer with KOAc. The impregnating stepmay occur prior to the exposing step, or that the impregnating step mayoccur after the exposing step. In any of the above embodiments, themethod may further include drying the support material subsequent to theimpregnating step.

In an aspect, a process is provided that includes contacting a reactantgas with the catalyst of any one of the above embodiments to producevinyl acetate monomer, where the reactant gas includes ethylene, aceticacid, and O₂.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates measurement parameters of an extrudate catalyst usedin an exemplary determination of the geometric surface area per packedbed volume of the extrudate catalyst.

FIG. 2 illustrates a representative distribution of lengths for anextrudate catalyst obtained in an exemplary determination of thegeometric surface area per packed bed volume of the extrudate catalyst.

FIG. 3 provides the correlation of the distribution of lengths providedin FIG. 2 with the respective mass of the individual extrudate catalystfor which the particular length was obtained, utilized in an exemplarydetermination of the geometric surface area per packed bed volume of anextrudate catalyst.

FIG. 4 provides a cross-section of a cored quadrilobe catalyst of thepresent technology where the dark bands adjacent to the support surfacecorrespond to the catalytic layer, according to an embodiment of thepresent technology.

DETAILED DESCRIPTION

The following terms are used throughout as defined below.

As used herein and in the appended claims, singular articles such as “a”and “an” and “the” and similar referents in the context of describingthe elements (especially in the context of the following claims) are tobe construed to cover both the singular and the plural, unless otherwiseindicated herein or clearly contradicted by context. Recitation ofranges of values herein are merely intended to serve as a shorthandmethod of referring individually to each separate value falling withinthe range, unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate the embodiments and does not pose a limitation on the scopeof the claims unless otherwise stated. No language in the specificationshould be construed as indicating any non-claimed element as essential.

As used herein, “about” will be understood by persons of ordinary skillin the art and will vary to some extent depending upon the context inwhich it is used. If there are uses of the term which are not clear topersons of ordinary skill in the art, given the context in which it isused, “about” will mean up to plus or minus 10% of the particular term.

Generally, reference to a certain element such as hydrogen or H is meantto include all isotopes of that element. For example, if an R group isdefined to include hydrogen or H, it also includes deuterium andtritium. Compounds comprising radioisotopes such as tritium, C¹⁴, P³²and S³⁵ are thus within the scope of the present technology. Proceduresfor inserting such labels into the compounds of the present technologywill be readily apparent to those skilled in the art based on thedisclosure herein.

As will be understood by one skilled in the art, for any and allpurposes, particularly in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as “up to,” “at least,” “greater than,” “less than,” and the likeinclude the number recited and refer to ranges which can be subsequentlybroken down into subranges as discussed above. Finally, as will beunderstood by one skilled in the art, a range includes each individualmember. Thus, for example, a group having 1-3 atoms refers to groupshaving 1, 2, or 3 atoms. Similarly, a group having 1-5 atoms refers togroups having 1, 2, 3, 4, or 5 atoms, and so forth.

“Substantially free” as used herein will be understood by persons ofordinary skill in the art and will vary to some extent depending uponthe context. If there are uses of the term which are not clear topersons of ordinary skill in the art, given the context in which it isused, “substantially free” will mean that the substance is at about 0.5wt % or less.

Catalysts have been identified and are described herein, that, when usedto produce vinyl acetate monomer (“VAM”), exhibit high catalyticactivity and high selectivity in producing VAM. The catalysts include asupport that includes an external surface, about 60 wt % to about 99 wt% silica, about 1.0 wt % to about 5.0 wt % alumina, and a catalyticlayer disposed within the support adjacent to the external surface,where the catalytic layer further includes Pd, Au, and potassium acetate(KOAc). In the catalyst, (a) the KOAc is from about 60 kg/m³ to about150 kg/m³ of the catalyst; or (b) the catalytic layer has an averagethickness from about 50 μm to about 150 μm, or (c) the KOAc is fromabout 60 kg/m³ to about 150 kg/m³ of the catalyst and the catalyticlayer has an average thickness from about 50 μm to about 150 μm. Thecatalyst exhibits a Brunauer-Emmett-Teller surface area of about 130m²/g to about 300 m²/g and a geometric surface area per packed bedvolume (GSA/PBV) from about 550 m²/m³ to about 1500 m²/m³. The catalystmay be an extrudate catalyst, a precipitate catalyst, or a sphere-likecatalyst. In some embodiments, the catalyst is an extrudate catalyst.Formation of extrudate catalysts typically includes pushing a pastethrough a die with or without cutting to length. Extrudate catalysts maybe formed with solid or hollow interiors; the exteriors of an extrudatecatalyst may have cross-sectional shape including, but not limited to,cylindrical, tubular, polylobular, ring, star, a trilobe, a quadrilobe,a cloverleaf shape, saddle, fluted, ridged, a multi-pointed star, afluted ring, a hallow cylinder, a cogwheel, a spoked wheel, a multi-holepellet, or a monolith.

The support includes from about 60 wt % to about 99 wt % silica. In anyembodiment herein, the support may include silica in an amount of about60 wt %, about 62 wt %, about 64 wt %, about 66 wt %, about 68 wt %,about 70 wt %, about 75 wt %, about 80 wt %, about 85 wt %, about 90 wt%, about 95 wt %, about 98 wt %, about 99 wt %, or any range includingand in between any two of these values. The support also includesalumina in an amount from about 1.0 wt % to about 5.0 wt %. The amountof alumina in the support may be about 1.0 wt %, about 1.2 wt %, about1.4 wt %, about 1.6 wt %, about 1.8 wt %, about 2.0 wt %, about 2.2 wt%, about 2.4 wt %, about 2.6 wt %, about 2.8 wt %, about 3.0 wt %, about3.2 wt %, about 3.4 wt %, about 3.6 wt %, about 3.8 wt %, about 4.0 wt%, about 4.2 wt %, about 4.4 wt %, about 4.6 wt %, about 4.8 wt %, about5.0 wt %, or any range including and in between any two of these values.For example, in any of the above embodiments, the alumina may be fromabout 1.0 wt % to about 3.0 wt %.

As noted above, the catalyst has a Brunauer-Emmett-Teller surface area(“BET surface area”) from about 130 m²/g to about 300 m²/g. The BETsurface area may be determined by several methods, including the methoddescribed in ASTM-D3663-03 (2008), incorporated herein by reference inits entirety for any and all purposes. The BET surface area may be about130 m²/g, about 140 m²/g, about 150 m²/g, about 160 m²/g, about 170m²/g, about 180 m²/g, about 190 m²/g, about 200 m²/g, about 210 m²/g,about 220 m²/g, about 230 m²/g, about 240 m²/g, about 250 m²/g, about260 m²/g, about 270 m²/g, about 280 m²/g, about 290 m²/g, about 300m²/g, or any range including and in between any two of these values. Forexample, in any of the above embodiments, the catalyst may have a BETsurface area from about 200 m²/g to about 250 m²/g.

The GSA/PBV excludes surface area provided by macro, meso, and micropores. While there are a variety of ways of determining GSA/PBV for thecatalysts, certain examples are provided below.

Geometric Surface Area (GSA)

For spherical catalysts, the geometric surface area (GSA) of a sphericalcatalyst is essentially 4π(r)², where “r” is the half of the diameter ofthe spherical catalyst.

For extrudate catalysts, the GSA may be assessed as follows. The outerperimeter (OP), inner perimeter (IP; when present), and face surfacearea (FSA) of the extrudate catalyst may be measured with a calibratedoptical microscope. FIG. 1 illustrates the outer perimeter, innerperimeter, face surface area (shaded), and length dimensions. The lengthof the extrudate catalyst may be measured using a micrometer. Usingthese measurements, the geometric surface area of a single extrudatecatalyst may be calculated as indicated in Equation 1.GSA=2*(FSA)+(IP)*Length+(OP)*Length   Eq. 1While FIG. 1 illustrates and Equation 1 describes the GSA of a catalystwith one void through the catalyst (a “hole”), if there are multipleholes in the face surface then the area attributed for each hole will beaccounted for when determining the GSA. For example, a catalyst with afirst hole with a IP₁ , and second hole with IP₂, and a third hole withIP₃ would have a GSA of2*(FSA)+(IP₁)*Length+(IP₂)*Length+(IP₃)*Length+(OP)*Length. Becauseextrudate catalysts are formed by passage through a regularly sized dieplate, the face surface area for all extrudate catalysts of a certaintype (e.g., shape) may be assumed constant. With a constant face surfacearea, the only parameter that may vary from one extrudate catalyst toanother is the length. To overcome this, a representative lengthdistribution may be utilized to determine the GSA.

To capture a representative length distribution, lengths may bedetermined for a number of extrudate catalysts greater than100*(standard deviation in length). For example, if the standarddeviation of measured lengths is 1.5, then 150 length measurements wouldbe used to obtain a reasonably representative distribution. FIG. 2provides an exemplary distribution curve for a cored quadrilobeextrudate catalyst according to the present technology with a diameterof about 5.5 mm at the longest point on the face surface. Using Equation1, the geometric surface area of each of the extrudate catalysts of thedistribution of extrudates may be calculated.

Geometric Surface Area Per Mass

To determine the geometric surface area per mass of catalyst from thisensemble of extrudate catalysts, a mass vs. length linear correlationmay be assessed by measuring the mass and length of >50 extrudates. Forextrudate catalyts, there is a strong correlation between the length andmass, as illustrated in FIG. 3 for the cored quadrilobe extrudatecatalyst used in FIG. 2. Using the length distribution in FIG. 2 and thelinear mass versus length correlation in FIG. 3, the geometric surfacearea per mass for the same distribution of 150 extrudate catalysts inFIG. 2 may be calculated, for example by using Equation 2. The “Mass ofParticle,” can be found from the linear mass versus length correlationin FIG. 3.

$\begin{matrix}{{\sum\limits_{i = 1}^{> 150}\frac{{GSA}_{i}}{{Mass}\mspace{14mu}{of}\mspace{14mu}{Particle}_{i}}} = \frac{{External}\mspace{14mu}{Surface}}{Mass}} & {{Eq}.\mspace{14mu} 2}\end{matrix}$A similar procedure may be used to determine a representative geometricsurface area per mass of a spherical catalyst. A representative value isachieved by using a large (at least greater than 50) ensemble ofparticles.Obtaining the GSA/PBV

To obtain the GSA/PBV utilizing the geometric surface area per mass, thepacked bed density of the catalyst type in question (e.g., a particularextrudate type, spherical catalyst, etc.) is measured. The packed beddensity may be determined by a variety of methods, including, but notlimited to, the method described in ASTM-D4164-82, incorporated hereinby reference in its entirety for any and all purposes. Multiplying thegeometric surface area per mass (in units of m²/g) with the packed beddensity (the “Mass/Volume” in units of g/m³), cancels the mass units toprovide the GSA/PBV, as shown in Equation 3.

$\begin{matrix}{{\frac{{External}\mspace{14mu}{Surface}}{Mass}*\frac{Mass}{Volume}} = \frac{{External}\mspace{14mu}{Surface}}{Volume}} & {{Eq}.\mspace{14mu} 3}\end{matrix}$Using the exemplary analysis provided above reasonably describes thegeometric surface area within a fixed packed bed volume of catalystparticles. However, it should be noted that other methods of determiningGSA/PBV may be utilized.

For the catalysts, the GSA/PBV may be about 550 m²/m³, about 560 m²/m³,about 570 m²/m³, about 580 m²/m³, about 590 m²/m³, about 600 m²/m³,about 625 m²/m³, about 650 m²/m³, about 675 m²/m³, about 700 m²/m³,about 725 m²/m³, about 750 m²/m³, about 775 m²/m³, about 800 m²/m³,about 825 m²/m³, about 850 m²/m³, about 875 m²/m³, about 900 m²/m³,about 950 m²/m³, about 1000 m²/m³, about 1100 m²/m³, about 1200 m²/m³,about 1300 m²/m³, about 1400 m²/m³, about 1500 m²/m³, about 1000 m²/m³,or any range including and in between any two of these values. Forexample, the catalyst may have a GSA/PBV that is from about 600 m²/m³ toabout 1500 m²/m³, or from about 800 m²/m³ to about 1300 m²/m³.

The KOAc is from about 60 kg/m³ to about 150 kg/m³ of the catalyst, andmay be about 60 kg/m³, about 65 kg/m³, about 70 kg/m³, about 75 kg/m³,about 80 kg/m³, about 85 kg/m³, about 90 kg/m³, about 95 kg/m³, about100 kg/m³, about 110 kg/m³, about 120 kg/m³, about 130 kg/m³, about 140kg/m³, about 150 kg/m³, or any range including and in between any two ofthese values. For example, in any of the above embodiments, the KOAc maybe from about 65 kg/m³ to about 100 kg/m³ of the catalyst.

In any of the above embodiments, the catalytic layer may have an averagethickness of about 50 μm to about 550 μm. Thus, the catalytic layer isdisposed within the support adjacent to the external surface of thesupport and extends inward towards the interior of the support. Theaverage thickness may be determined by using a calibrated opticalmicroscope to measure the dark band on the outside of a cross-section ofthe catalyst particles. FIG. 4 illustrates a cross-section of a coredquadrilobe catalyst, where the dark bands on the periphery adjacent tothe external surface correspond to the catalytic layer within thecatalyst. While a variety of methods of determining the averagethickness of the catalyst layer may be utilized, one approach includesmeasuring the catalytic layer thickness of ten (10) equidistant pointsof each external surface of the catalyst particle cross-section. Forexample, for the cored quadrilobe catalyst of FIG. 4 such measurementsinclude measuring the catalytic layer thickness in the hole at thecenter as well as on the face. The average thickness of the catalyticlayer of this cored quadrilobe catalyst may be determined by calculatingthe average of ten (10) equidistant catalytic layer thicknessmeasurements from the cross section and ten (10) points from theextrudate face. For a spherical catalyst, the average thickness may bedetermined by calculating the average of ten (10) equidistant catalyticlayer thickness measurements from the bisection of the sphericalcatalyst.

In the catalysts, the average thickness of the catalytic layer may beabout 50 μm, about 55 μm, about 60 μm, about 65 μm, about 70 μm, about75 μm, about 80 μm, about 85 μm, about 90 μm, about 95 μm, about 100 μm,about 110 μm, about 120 μm, about 130 μm, about 140 μm, about 150 μm,about 160 μm, about 170 μm, about 180 μm, about 190 μm, about 200 μm,about 210 μm, about 220 μm, about 230 μm, about 240 μm, about 250 μm,about 260 μm, about 270 μm, about 280 μm, about 290 μm, about 300 μm,about 310 μm, about 320 μm, about 330 μm, about 340 μm, about 350 μm,about 360 μm, about 370 μm, about 380 μm, about 390 μm, about 400 μm,about 410 μm, about 420 μm, about 430 μm, about 440 μm, about 450 μm,about 460 μm, about 470 μm, about 480 μm, about 490 μm, about 500 μm,about 510 μm, about 520 μm, about 530 μm, about 540 μm, about 550 μm, orany range including and in between any two of these values.

The amount of Pd in the catalyst may be from about 3 g/L to about 15g/L. The amount of Pd in the catalyst may be from about 3 g/L, about 4g/L, about 5 g/L, about 6 g/L, about 7 g/L, about 8 g/L, about 9 g/L,about 10 g/L, about 11 g/L, about 12 g/L, about 13 g/L, about 14 g/L,about 15 g/L, or any range including and in between any two of thesevalues. In any of the above embodiments, the Au in the catalyst may befrom about 0.9 g/L to about 7.0 g/L; the amount of Au in the catalystmay be about 0.9 g/L, about 1.0 g/L, about 1.1 g/L, about 1.2 g/L, about1.3 g/L, about 1.4 g/L, about 1.5 g/L, about 1.6 g/L, about 1.7 g/L,about 1.8 g/L, about 1.9 g/L, about 2.0 g/L, about 2.2 g/L, about 2.4g/L, about 2.6 g/L, about 2.8 g/L, about 3.0 g/L, about 3.2 g/L, about3.4 g/L, about 3.6 g/L, about 3.8 g/L, about 4.0 g/L, about 4.2 g/L,about 4.4 g/L, about 4.6 g/L, about 4.8 g/L, about 5.0 g/L, about 5.5g/L, about 6.0 g/L, about 6.5 g/L, about 7.0 g/L, or any range includingand in between any two of these values.

The mass ratio of Pd to Au may be from about 3.5:1 to about 2.0:1. Themass ratio of Pd to Au in any of the above embodiments may be about3.5:1, about 3.4:1, about 3.3:1, about 3.2:1, about 3.1:1, about 3.0:1,about 2.9:1, about 2.8:1, about 2.7:1, about 2.6:1, about 2.5:1, about2.4:1, about 2.3:1, about 2.2:1, about 2.1:1, about 2.0:1, or any rangeincluding and in between any two of these values.

The void fraction of the catalyst may be from about 35% to about 55%.Void fraction is the measure of the empty space in the catalyst andbetween individual catalysts when packed in a fixed bed, where the voidfraction is the void volume in the packed fixed bed divided by thevolume of the fixed bed. The void volume may be determined by a varietyof methods, including, but not limited to, ASTM CCA11916, ASTM D6761-07,ASTM D5965-02, or ASTM C604-02. Thus, the void volume includes the emptyspace within the catalyst from features such as holes and depressions aswell as between individual catalysts in a packed fixed bed. The voidfraction of the catalyst may be about 35%, about 36%, about 37%, about38%, about 39%, about 40%, about 42%, about 44%, about 46%, about 48%,about 50%, about 51%, about 52%, about 53%, about 54%, about 55%, or anyrange including and in between any two of these values.

The catalyst may be in a shape including, but not limited to, at leastone of cylindrical, spherical, tubular, polylobular, ring, star, saddle,fluted, or ridged. Examples of such shapes include, but not limited to,a Raschig ring, a Pall ring, a Berl saddle, a Intalox saddle, atrilobes, a quadrilobes, a cloverleaf shape, a multi-lobed shape, amulti-pointed star, a fluted ring, a hallow cylinder, a cogwheel, aspoked wheel, a multi-hole pellets, or a monolith. In any of the aboveembodiments, the catalyst may have a diameter from about 2.0 millimeters(“mm”) to about 9.0 mm. The diameter of the catalyst may be about 2.0mm, about 2.1 mm, about 2.2 mm, about 2.3 mm, about 2.4 mm, about 2.5mm, about 2.6 mm, about 2.7 mm, about 2.8 mm, about 2.9 mm, about 3.0mm, about 3.1 mm, about 3.2 mm, about 3.3 mm, about 3.4 mm, about 3.5mm, about 3.6 mm, about 3.7 mm, about 3.8 mm, about 3.9 mm, about 4.0mm, about 4.1 mm, about 4.2 mm, about 4.3 mm, about 4.4 mm, about 4.5mm, about 4.6 mm, about 4.7 mm, about 4.8 mm, about 4.9 mm, about 5.0mm, about 5.1 mm, about 5.2 mm, about 5.3 mm, about 5.4 mm, about 5.5mm, about 5.6 mm, about 5.7 mm, about 5.8 mm, about 5.9 mm, about 6.0mm, about 6.1 mm, about 6.2 mm, about 6.3 mm, about 6.4 mm, about 6.5mm, about 6.6 mm, about 6.7 mm, about 6.8 mm, about 6.9 mm, about 7.0mm, about 7.1 mm, about 7.2 mm, about 7.3 mm, about 7.4 mm, about 7.5mm, about 7.6 mm, about 7.7 mm, about 7.8 mm, about 7.9 mm, about 8.0mm, about 8.1 mm, about 8.2 mm, about 8.3 mm, about 8.4 mm, about 8.5mm, about 8.6 mm, about 8.7 mm, about 8.8 mm, about 8.9 mm, about 9.0mm, or any range including and in between any two of these values.

While the catalytic layer may include Pd, Au, and KOAc, the remainingsupport may be substantially free of Pd, Au, and KOAc. In any of theabove embodiments, the amount of Pd in the support (not including thecatalytic layer) may be less than about 0.4 wt %, less than about 0.3 wt%, less than about 0.2 wt %, less than about 0.1 wt %, or any rangeincluding and in between any two of these values. In any of the aboveembodiments, the amount of Au in the support (not including thecatalytic layer) may be less than about 0.4 wt %, less than about 0.3 wt%, less than about 0.2 wt %, less than about 0.1 wt %, or any rangeincluding and in between any two of these values. In any of the aboveembodiments, the amount of KOAc in the support (not including thecatalytic layer) may be less than about 0.4 wt %, less than about 0.3 wt%, less than about 0.2 wt %, less than about 0.1 wt %, or any rangeincluding and in between any two of these values.

In an aspect, method of making any one of the previously describedcatalysts is provided. The method includes permeating a support material(which includes an external surface with Pd and Au) to provide ametal-containing layer disposed within the support material adjacent tothe external surface. The support material includes about 60 wt % toabout 99 wt % silica, and about 1.0 wt % to about 5.0 wt % alumina, andthe metal-containing layer further includes Pd and Au. The amount ofsilica, alumina, Pd, and Au may be any one or more of the previouslydiscussed values.

In some embodiments, permeating the support material includes contactingthe support material with a salt solution that includes a salt of Pd, asalt of Au, or a mixture thereof. In any of the above embodiments, thesalt solution may include a chloride salt of Pd, a chloride salt of Au,or a mixture thereof. In any of the above embodiments, the solution maybe an aqueous solution. In any of the above embodiments, the salt of Pdmay be palladium (II) chloride, sodium palladium (II) chloride,palladium (II) nitrate, or a mixture of any two or more thereof. In anyof the above embodiments, the salt of Au may be gold (III) chloride,tetrachloroauric (III) acid, or a mixture thereof.

In any of the above embodiments, subsequent to contacting with the saltsolution, permeating the support material may include contacting thesupport material with a basic solution. The basic solution may beaqueous and may include sodium metasilicate. In any of the aboveembodiments, the method further include a washing step subsequent to thepermeating step.

In any of the above embodiments, the method may further include dryingthe support material subsequent to the permeating step. In any of theabove embodiments, drying subsequent to the permeating step may occur ata temperature from about 40° C. to about 250° C. Drying subsequent tothe permeating step may occur at a temperature of about 40° C., about50° C., about 60° C., about 70° C., about 80° C., about 90° C., about100° C., about 125 ° C., about 150° C., about 175° C., about 200° C.,about 225° C., about 250° C., or any range including and in between anytwo of these values. In any of the above embodiments, the dryingsubsequent to the permeating step may occur under vacuum. In any of theabove embodiments, it may be that the method further includes drying thesupport material subsequent to the washing step. In any of the aboveembodiments, it may be that drying subsequent to the washing step occursat a temperature from about 40° C. to about 250° C. Drying subsequent tothe washing step may occur at a temperature of about 40° C., about 50°C., about 60° C., about 70° C., about 80° C., about 90° C., about 100°C., about 125° C., about 150° C., about 175° C., about 200° C., about225° C., about 250° C., or any range including and in between any two ofthese values. In any of the above embodiments, the drying subsequent tothe washing step may occur under vacuum. In any of the aboveembodiments, the drying subsequent to the washing step may occur underan inert atmosphere.

The method may further include exposing the metal-containing layer to areducing agent. The reducing agent may include a reduction gas, wherethe reduction gas may include H₂. In any of the above embodiments, thereducing gas may include about 4% to about 100% H₂ on a molar basis. Thereduction gas may include H₂ in an amount of about 4%, about 5%, about6%, about 7%, about 8%, about 9%, about 10%, about 20%, about 30%, about40%, about 50%, about 60%, about 70%, about 80%, about 90%, about 95%,about 98%, about 99%, about 100%, or any range including and in betweenany two of these values. The reducing gas may further include nitrogengas, ethylene, or a mixture thereof. In embodiments where the reductiongas includes H₂ and nitrogen gas, the nitrogen gas and H₂ may be presentin a ratio from about 5:1 to 1:1. The duration of the exposing step maybe about 1 hour, about 2 hours, about 3 hours, about 4 hours, or anyrange including and in between any two of these values. The exposingstep may occur at a temperature from about 15° C. to about 500° C.;thus, the exposing step may occur at a temperature of about 15° C.,about 20° C., about 25° C., about 30° C., about 35° C., about 40° C.,about 45° C., about 50° C., about 55° C., about 60° C., about 70° C.,about 80° C., about 90° C., about 100° C., about 125° C., about 150° C.,about 175° C., about 200° C., about 225° C., about 250° C., about 275°C., about 300° C., about 350° C., about 400° C., about 450° C., about500° C., or any range including an in between any two of these values.For example, the exposing step may occur at a temperature from about175° C. to about 500° C.

The method may further include impregnating the metal-containing layerwith KOAc. The impregnating step may occur prior to the exposing step,or that the impregnating step occurs after the exposing step. Theimpregnating step may include contacting the metal containing layer withan aqueous solution of KOAc. In any of the above embodiments, the methodmay further include drying the support material subsequent to theimpregnating step. Drying subsequent to the impregnating step may occurat a temperature of about 40° C., about 50° C., about 60° C., about 70°C., about 80° C., about 90° C., about 100° C., about 125° C., about 150°C., about 175° C., about 200° C., about 225° C., about 250° C., or anyrange including and in between any two of these values. In any of theabove embodiments, the drying subsequent to the impregnating step mayoccur under vacuum. In any of the above embodiments, the dryingsubsequent to the impregnating step may occur under an inert atmosphere.

In an aspect, a process is provided that includes contacting a reactantgas with the catalyst of any one of the above embodiments to producevinyl acetate monomer, where the reactant gas includes ethylene, aceticacid, and O₂. The contacting step may be contained within a fixedbed-type reactor that contains the catalyst. In such embodiments, it maybe that the reactant gas flows through the fixed bed-type reactorcontaining the catalyst, where such flow accomplishes contacting thereactant gas with the catalyst.

However, the catalysts of the present technology may be used in otherreactions, including (but not limited to) those involving an olefin,oxygen, and a carboxylic acid.

The examples herein are provided to illustrate advantages of the presenttechnology and to further assist a person of ordinary skill in the artwith preparing or using the present technology. The examples herein arealso presented in order to more fully illustrate the preferred aspectsof the present technology. The examples should in no way be construed aslimiting the scope of the present technology, as defined by the appendedclaims. The examples can include or incorporate any of the variations,aspects or aspects of the present technology described above. Thevariations, aspects or aspects described above may also further eachinclude or incorporate the variations of any or all other variations,aspects or aspects of the present technology.

EXAMPLES

While certain embodiments have been illustrated and described, a personwith ordinary skill in the art, after reading the foregoingspecification, can effect changes, substitutions of equivalents andother types of alterations to the compounds of the present technology.Each aspect and embodiment described above can also have included orincorporated therewith such variations or aspects as disclosed in regardto any or all of the other aspects and embodiments.

Composition of Exemplary Catalyst of Present Technology and aComparative Catalyst. The compositions and properties of two catalystsof the present technology (Catalyst 1 and Catalyst 2) and a ComparativeCatalyst (“Comparative”) are provided in Table 1 below. SiO₂ and Al₂O₃were determined by X-ray florescence with a detection limit of ˜0.1 wt%. Pd, Au, and K were determined by inductively coupled plasma atomicemission spectroscopy. All potassium measured was assumed to be frompotassium acetate.

TABLE 1 Comparative Catalyst 1 Catalyst 2 SiO₂ (wt %) 96.4 96.4 96.0Al₂O₃ (wt %) 1.6 1.6 2.0 KOAc (kg/m³) 40 40 61.7 Pd (g/L) 6.00 6.09 5.61Au (g/L) 2.60 2.65 2.23 BET surface 255 255 230 area (m²/g) Geometric643 643 1042 Surface Area (m²/m³) Void Fraction 39.8 39.8 51.5 (%)Packed ambient 0.40 0.40 0.32 bulk density (g/cc) Thickness of 300 μm 120 μm  120 μm  catalytic layer (μm) Diameter 5.8 mm 5.8 mm 6.6 mm ShapeSpherical Spherical Polylobular, non-tubular N.D. = Not Detected

Improvements in Space-Time-Yield and Selectivity. VAM production wasevaluated in an isothermal fixed-bed reactor with silicon carbidefilling the catalyst particle void space to eliminate gas channeling,where the results of FIGS. 1 and 2 are after 20 hours of operation at150° C. The operating conditions for the reactor are provided in Table2.

TABLE 2 Temperature 150° C. Pressure 8.27 bar GHSV 35,000 hr⁻¹ CatalystBed Volume 7.15 mLThe reactant feed to the reactor was 79.24 mol % ethylene, 12.04 mol %acetic acid, 6.6 mol % O₂, and 2.11 mol % water. The space-time-yieldand vinyl acetate selectivity are provided in Table 3 below.

TABLE 3 Normalized Space-Time- Yield at 95% Vinyl Vinyl AcetateSelectivity (%) Acetate Selectivity at 200 g VAM/[(g Pd)(hr)]Comparative 1 94.75 Catalyst 1 1.25 95.59 Catalyst 2 1.44 95.82The space-time-yield is calculated to correct for differences in metalloading between the catalysts and was normalized with respect to theComparative Catalyst. As shown in Table 3, Catalysts 1 and 2 aresignificantly more active catalysts than the Comparative Catalyst, whereCatalyst 2 is more active than Catalyst 1. In addition, Catalysts 1 and2 provide a significantly greater selectivity for vinyl acetate.

The present technology is also not to be limited in terms of theparticular aspects described herein, which are intended as singleillustrations of individual aspects of the present technology. Manymodifications and variations of this present technology can be madewithout departing from its spirit and scope, as will be apparent tothose skilled in the art. Functionally equivalent methods within thescope of the present technology, in addition to those enumerated herein,will be apparent to those skilled in the art from the foregoingdescriptions. Such modifications and variations are intended to fallwithin the scope of the appended claims. It is to be understood thatthis present technology is not limited to particular methods, reagents,compounds, compositions, labeled compounds or biological systems, whichcan, of course, vary. It is also to be understood that the terminologyused herein is for the purpose of describing particular aspects only,and is not intended to be limiting. Thus, it is intended that thespecification be considered as exemplary only with the breadth, scopeand spirit of the present technology indicated only by the appendedclaims, definitions therein and any equivalents thereof.

The embodiments, illustratively described herein may suitably bepracticed in the absence of any element or elements, limitation orlimitations, not specifically disclosed herein. Thus, for example, theterms “comprising,” “including,” “containing,” etc. shall be readexpansively and without limitation. Additionally, the terms andexpressions employed herein have been used as terms of description andnot of limitation, and there is no intention in the use of such termsand expressions of excluding any equivalents of the features shown anddescribed or portions thereof, but it is recognized that variousmodifications are possible within the scope of the claimed technology.Additionally, the phrase “consisting essentially of” will be understoodto include those elements specifically recited and those additionalelements that do not materially affect the basic and novelcharacteristics of the claimed technology. The phrase “consisting of”excludes any element not specified.

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group. Each of the narrowerspecies and subgeneric groupings falling within the generic disclosurealso form part of the invention. This includes the generic descriptionof the invention with a proviso or negative limitation removing anysubject matter from the genus, regardless of whether or not the excisedmaterial is specifically recited herein.

All publications, patent applications, issued patents, and otherdocuments (for example, journals, articles and/or textbooks) referred toin this specification are herein incorporated by reference as if eachindividual publication, patent application, issued patent, or otherdocument was specifically and individually indicated to be incorporatedby reference in its entirety. Definitions that are contained in textincorporated by reference are excluded to the extent that theycontradict definitions in this disclosure.

The present technology includes, but is not limited to, the followinglettered paragraphs:

-   A. A catalyst comprising:    -   a support comprising:        -   an external surface;        -   about 60 wt % to about 99 wt % silica; and        -   about 1.0 wt % to about 5.0 wt % alumina;    -   a catalytic layer disposed within the support adjacent to the        external surface,        -   where the catalytic layer further comprises Pd, Au, and            potassium acetate (KOAc);    -   a Brunauer-Emmett-Teller surface area of about 130 m²/g to about        300 m²/g;        -   and    -   a geometric surface area per packed bed volume from about 550        m²/m³ to about 1500 m²/m³;    -   wherein        -   (a) the KOAc is from about 60 kg/m³ to about 150 kg/m³ of            the catalyst; or        -   (b) the catalytic layer has an average thickness from about            50 μm to about 150 μm, or        -   (c) the KOAc is from about 60 kg/m³ to about 150 kg/m³ of            the catalyst and the catalytic layer has an average            thickness from about 50 μm to about 150 μm.-   B. The catalyst of Paragraph A, wherein the KOAc is from about 65    kg/m³ to about 100 kg/m³ of the catalyst.-   C. The catalyst of Paragraph A or B, wherein the catalytic layer has    an average thickness from about 50 μm to about 550 μm.-   D. The catalyst of any one of Paragraphs A-C, wherein the catalytic    layer has an average thickness from about 100 μm to about 400 μm.-   E. The catalyst of any one of Paragraphs A-D, wherein the catalytic    layer has an average thickness from about 100 μm to about 200 μm.-   F. The catalyst of any one of Paragraphs A-E, wherein the alumina is    from about 1.0 wt % to about 3.0 wt %.-   G. The catalyst of any one of Paragraphs A-F, wherein the Pd in the    catalyst is from about 3 g/L to about 15 g/L.-   H. The catalyst of any one of Paragraphs A-G, wherein the Au in the    catalyst is from about 0.9 g/L to about 7.0 g/L.-   I. The catalyst of any one of Paragraphs A-H, wherein the mass ratio    of Pd to Au is from about 3.5:1 to about 2.0:1.-   J. The catalyst of any one of Paragraphs A-I, wherein the    Brunauer-Emmett-Teller surface area of the catalyst is from about    200 m²/g to about 250 m²/g.-   K. The catalyst of any one of Paragraphs A-J, wherein the geometric    surface area per packed bed volume of the catalyst is from about 600    m²/m³ to about 1500 m²/m³.-   L. The catalyst of any one of Paragraphs A-K, wherein the geometric    surface area per packed bed volume of the catalyst is from about 800    m²/m³ to about 1300 m²/m³.-   M. The catalyst of any one of Paragraphs A-L, wherein the void    fraction of the catalyst is from about 35% to about 55%.-   N. The catalyst of any one of Paragraphs A-M, wherein the catalyst    is in a shape comprising at least one of cylindrical, spherical,    tubular, polylobular, ring, star, saddle, fluted, or ridged.-   O. The catalyst of any one of Paragraphs A-N, wherein with the    exception of the catalytic layer, the support is substantially free    of Pd, Au, and KOAc.-   P. A method of making the catalyst of any one of Paragraphs A-O, the    method comprising permeating a support material comprising an    external surface with Pd and Au to provide a metal-containing layer    disposed within the support material adjacent to the external    surface; wherein    -   the support material comprises:        -   about 60 wt % to about 99 wt % silica; and        -   about 1.0 wt % to about 5.0 wt % alumina;    -   the metal-containing layer further comprises Pd and Au.-   Q. The method of Paragraph P, wherein permeating the support    material comprises contacting the support material with a salt    solution comprising a salt of Pd, a salt of Au, or a mixture    thereof.-   R. The method of Paragraph Q, wherein subsequent to contacting with    the salt solution, permeating the support material comprises    contacting the support material with a basic solution.-   S. The method of any one of Paragraphs P-R, further comprising a    washing step subsequent to the permeating step.-   T. The method of any one of Paragraphs P-S, further comprising    drying the support material subsequent to the permeating step.-   U. The method of Paragraph T, wherein drying subsequent to the    permeating step occurs at a temperature from about 40° C. to about    250° C.-   V. The method of any one of Paragraphs S-U, further comprising    drying the support material subsequent to the washing step.-   W. The method of Paragraph V, wherein drying subsequent to the    washing step occurs at a temperature from about 40° C. to about 250°    C.-   X. The method of any one of Paragraphs P-W, further comprising    exposing the metal-containing layer to a reducing agent.-   Y. The method of Paragraph X, wherein the exposing step occurs at a    temperature from about 15° C. to about 500° C.-   Z. The method of any one of Paragraphs P-Y, wherein the method    further comprises impregnating the metal-containing layer with KOAc.-   AA. The method of Paragraph Z, wherein the impregnating step occurs    before the exposing step.-   AB. The method of Paragraph Z, wherein the impregnating step occurs    after the exposing step.-   AC. The method of any one of Paragraphs Z-AB, further comprising    drying the support material subsequent to the impregnating step.-   AD. A process comprising contacting a reactant gas with the catalyst    of any one of Paragraphs A-O to produce vinyl acetate monomer;    wherein the reactant gas comprises ethylene, acetic acid, and O₂.

Other embodiments are set forth in the following claims, along with thefull scope of equivalents to which such claims are entitled.

What is claimed is:
 1. A catalyst comprising: a support comprising: anexternal surface; about 60 wt % to about 99 wt % silica; and about 1.0wt % to about 5.0 wt % alumina; a catalytic layer disposed within thesupport adjacent to the external surface, where the catalytic layerfurther comprises Pd, Au, and potassium acetate (KOAc); and wherein thecatalytic layer has an average thickness from about 50 μm to about 200μm; a Brunauer-Emmett-Teller surface area of about 130 m²/g to about 300m²/g; and a geometric surface area per packed bed volume from about 550m²/m³ to about 1500 m²/m³; wherein (a) the KOAc is from about 60 kg/m³to about 150 kg/m³ of the catalyst; or (b) the catalytic layer has anaverage thickness from about 50 μm to about 150 μm, or (c) the KOAc isfrom about 60 kg/m³ to about 150 kg/m³ of the catalyst and the catalyticlayer has an average thickness from about 50 μm to about 150 μm.
 2. Thecatalyst of claim 1, wherein the KOAc is from about 65 kg/m³ to about100 kg/m³ of the catalyst.
 3. The catalyst of claim 1, wherein thealumina is present in the catalyst from about 1.0 wt % to about 3.0 wt %, Pd is present in the catalyst is from about 3 g/L to about 15 g/L, andthe Au is present in the catalyst is from about 0.9 g/L to about 7.0g/L.
 4. The catalyst of claim 1, wherein the mass ratio of Pd to Au isfrom about 3.5:1 to about 2.0:1.
 5. The catalyst of claim 1, wherein theBrunauer-Emmett-Teller surface area of the catalyst is from about 200m²/g to about 250 m²/g.
 6. The catalyst of claim 1, wherein thegeometric surface area per packed bed volume of the catalyst is fromabout 800 m²/m³ to about 1300 m²/m³.
 7. The catalyst of claim 1, whereinwith the exception of the catalytic layer, the support is substantiallyfree of Pd, Au, and KOAc.
 8. The catalyst of claim 1, wherein the KOAcis from about 65 kg/m³ to about 100 kg/m³ of the catalyst and thecatalytic layer has an average thickness from about 50 μm to about150μm.
 9. The catalyst of claim 8, wherein the catalyst is of a shapeselected from cylindrical, spherical, tubular, polylobular, ring, star,saddle, fluted, or ridged.
 10. The catalyst of claim 1, wherein the KOAcis from about 65 kg/m³ to about 100 kg/m³ of the catalyst; the catalyticlayer has an average thickness from about 50 μm to about 150μm; and thegeometric surface area per packed bed volume of the catalyst is fromabout 600 m²/m³ to about 1500 m²/m³.
 11. A method of making the catalystof claim 1, the method comprising permeating a support materialcomprising an external surface with Pd and Au to provide ametal-containing layer disposed within the support material adjacent tothe external surface; wherein the support material comprises: about60 wt% to about 99 wt % silica; and about 1.0 wt % to about 5.0 wt % alumina;the metal-containing layer further comprises Pd and Au.
 12. The methodof claim 11, wherein permeating the support material comprisescontacting the support material with a salt solution comprising a saltof Pd, a salt of Au, or a mixture thereof.
 13. The method of claim 12,wherein subsequent to contacting with the salt solution, permeating thesupport material comprises contacting the support material with a basicsolution.
 14. The method of claim 11, further comprising exposing themetal-containing layer to a reducing agent.
 15. The method of claim 14,wherein the exposing step occurs at a temperature from about 15° C. toabout 500° C.
 16. The method of claim 11, wherein the method furthercomprises impregnating the metal-containing layer with KOAc.
 17. Aprocess comprising contacting a reactant gas with the catalyst of claim1 to produce vinyl acetate monomer; wherein the reactant gas comprisesethylene, acetic acid, and O₂.